House Robber II

Problem

After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, the security system for these houses remain the same as for those in the previous street.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.

Notice: This is an extension of House Robber.

Example

nums = [3,6,4], return 6

Code - Java

public class Solution {
    /**
     * @param nums: An array of non-negative integers.
     *              return: The maximum amount of money you can rob tonight
     */
    public int houseRobber2(int[] nums) {
        if (nums.length == 0) return 0;
        if (nums.length == 1) return nums[0];
        if (nums.length == 2) return Math.max(nums[0], nums[1]);
        return Math.max(calc(nums, 0, nums.length - 2), calc(nums, 1, nums.length - 1));
    }

    private int calc(int[] nums, int left, int right) {
        int[] dp = new int[nums.length];

        dp[left] = nums[left];
        dp[left + 1] = Math.max(nums[left], nums[left + 1]);
        for (int i = left + 2; i <= right; i++) {
            dp[i] = Math.max(dp[i - 2] + nums[i], dp[i - 1]);
        }
        return dp[right];
    }
}